1. Field of the Invention
The present invention relates to an image forming unit for forming an image on a recording medium supplied from a storage tray, and an image forming apparatus having the image forming unit, and particularly relates to an image forming unit to which storage trays having various storage capacities can be removably attached in accordance with the need of users in spite of easiness in design or molding and reduction in cost, and an image forming apparatus having the image forming unit.
2. Background Art
An image forming apparatus such as a printer includes a process unit, a fixing unit, a scanner, and so on as a printing device. Under the printing device, a storage tray for storing sheets of paper as recording media is provided removably. The sheets of paper in the storage tray are fed one by one to an printing device by a paper supply roller disposed above the storage tray or other rollers. Thus, printing is performed on the sheets of paper.
In some of the printers configured thus, another optional tray unit can be additionally attached in accordance with the need of a user (see JP-A-5-17034, page 3 and FIG. 1). That is, the tray unit has another storage tray separate from the storage tray provided in the printer. When the tray unit is additionally attached to the printer, the paper storage capacity is increased so that the frequency of paper replenishment can be reduced.
In such a manner, the frequency of paper replenishment can be reduced by adding a tray unit suitably in accordance with the use conditions. To this end, however, users have to purchase tray units and attach them severally. To solve such labor, it can be therefore considered to manufacture and provide printers for a plurality of models different only in the paper storage capacity of the storage tray. Thus, users can choose printers in accordance with their needs respectively. This solution is very user-friendly because users do not have to purchase tray units and attach them severally.
Here, in order to design printers for a plurality of models different only in the paper storage capacity of the storage tray, configurations as shown in FIGS. 8A and 8B may be considered. FIGS. 8A and 8B are diagrams showing the overall configurations of the printers for a plurality of models different only in the paper storage capacity of the storage tray. First, a printer 500 shown in FIG. 8A has a printing device 50 such as a process unit, and a storage tray 506 lying under the printing device 50 and having a certain storage capacity. Both the printing device 50 and the storage tray 506 are supported by frames 552 from their opposite (left and right) sides. Tray guides 561 for supporting the storage tray 506 from the opposite (left and right) sides of the paper of FIG. 8A and supporting the weight of the printing device 50 are disposed between the storage tray 506 and the frames 552 respectively. A cover 553 is provided to cover the outsides of the frames 552.
On the other hand, a printer 600 shown in FIG. 8B has a storage tray 606 having a paper storage capacity larger than that of the storage tray 506 depicted in FIG. 8A. Further, the printer 600 has tray guides 661, a printing device 50 and frames 652 and a cover 653 in the same manner as the printer 500 depicted in FIG. 8A. That is, the tray guides 661 support the storage tray 606 from the opposite (left and right) sides of the paper of FIG. 8B and support the weight of the printing device 50. The frames 652 support the printing device 50 and the tray guides 661. The cover 653 is located outermost.